In an electronic device, a detection circuit is essential to detect whether the battery is connected to the charger within the electronic device or not. After the detection circuit confirms that the battery is connected with the charger and an external power source is connected to the electronic device, the charger can perform a charging operation base on battery charge capacity. The electronic device is for example a notebook computer, a personal digital assistant (PDA), a mobile phone, or the like.
FIG. 1 is a schematic timing diagram illustrating a charging current and a terminal voltage of a battery for an electronic device according to the prior art. Generally, the electronic device has a charger. According to the residual charge capacity, the charger may perform a charging operation. During the charging operation is performed, the charging process may be divided into three phases, including a trickle charge phase, a constant current charge phase and a constant voltage charge phase.
Please refer to FIG. 1 again. In a case that the residual charge capacity is very low, the charger is operated in the trickle charge phase to charge the battery at a low constant current I1. During the trickle charge phase, the battery voltage is gradually increased. After the battery voltage is increased to a first voltage V1, the charger is operated in the constant current charge phase to charge the battery at a high constant current I2. During the constant current charge phase, the voltage is also gradually increased. After the battery voltage is increased to a regulation voltage Vr, the charger is operated in the constant voltage charge phase to charge the battery at the regulation voltage Vr. During the constant voltage charge phase, the battery current is gradually decreased as the residual charge capacity of the batter is increased.
FIGS. 2A and 2B are schematic timing diagrams illustrating operations of the conventional charger when the battery is unplugged from electronic device. As shown in FIGS. 2A and 2B, a charging current I3 is provided by the charger to charge the battery, wherein the charging voltage is V3. At the time spot t1, the battery is removed from the electronic device, and the battery is in the unplugged status. Meanwhile, according to the charging status of the battery, the charging voltage is increased or decreased by ΔV, and the charging current is reduced to zero.
FIG. 3 is a schematic circuit diagram illustrating a charging control system for detecting battery removal or absent battery condition in a constant current charger according to the prior art. This charging control system is disclosed in U.S. Pat. No. 6,340,876. As shown in FIG. 3, the charging control system 100 comprises an input power source Vin, a battery 150, a charger 102, a state machine 106, and a detection circuit 10. The detection circuit 10 comprises several logic circuits and two comparators for generating a ΔGONE signal 16 and a ΔVCH signal 14.
After the battery 150 is removed from the charger 102, the charging voltage at output terminal (OUT) of the charger 102 is increased, so that the ΔVCH signal 14 is outputted from the detection circuit 10. In addition, the current through the input terminal (IN) of the charger 102 will be decreased, so that the ΔGONE signal 16 is outputted from the detection circuit 10. According to the ΔGONE signal 16 and the ΔVCH signal 14, the logic circuits of the detection circuit 10 will generate a battery absence signal (NO_BAT). The operating principles of the detection circuit 10 are known in the art, and are not redundantly described herein. According to the battery absence signal (NO_BAT), it is realized that the battery 150 is removed.
From the above discussions, the charging control system uses additional logic circuits to detect whether the battery is removed during the battery 150 is charged by the charger 102. However, the charging control system of this embodiment fails to detect whether the battery is really connected to (or plugged into) the charger 102.
FIG. 4 is a schematic circuit diagram illustrating a battery detector disclosed in U.S. Pat. No. 6,420,854. As shown in FIG. 4, the battery detector 200 comprises a charger 202, an indicator circuit 211, a battery 208, a resistor 210, and an inductor 204. The indicator circuit 211 comprises a capacitor (C) 214, a relay (R) 212, and a transistor 216. A pulse signal is continuously received by a base terminal (VB) of the transistor 216.
In a case that the battery 208 is removed from the battery detector 200, the voltage across the two ends of the capacitor 214 fails to energize the relay 212. On the contrary, after the battery 208 is plugged into the battery detector 200, the voltage across the two ends of the capacitor 214 is sufficient to energize the relay 212. In other words, the energized status and non-energized status of the relay 212 may be employed to judge whether the battery 208 is plugged into or unplugged from the battery detector 200.
However, after the relay 212 is energized, the electric energy is provided by the battery 208. In other words, after the battery 208 is plugged into the battery detector 200, the battery 208 still consumes charge continuously.
Recently, as the battery manufacturing technique is increasingly developed, a lithium battery module is used as the battery of the electronic device to gradually replace the conventional chargeable battery. If the charge capacity of the lithium battery module is very low, it is necessary to force the lithium battery module to stop continuously outputting the charge. Otherwise, the chemical reaction occurring in the lithium battery module may result in a permanent damage of the lithium battery module. FIG. 5 is a schematic circuit diagram illustrating a conventional lithium battery module. As shown in FIG. 5, the lithium battery module 500 comprises a controlling circuit 510, a transistor 520, and a lithium battery set 530. The controlling circuit 510 is connected with the lithium battery set 530 for detecting whether the residual charge quantity of the lithium battery set 530 reaches a threshold charge quantity. If the residual charge quantity of the lithium battery set 530 is not lower than the threshold charge quantity, in response to a control signal from the control terminal C of the controlling circuit 510, the transistor 520 is turned on. Consequently, the lithium battery set 530 of the lithium battery module 500 can output electric energy to the electronic device through the positive terminal (+) and the negative terminal (−). Whereas, if the residual charge quantity of the lithium battery set 530 is continuously consumed to be lower than the threshold charge quantity, in response to a control signal from the control terminal C of the controlling circuit 510, the transistor 520 is turned off. Consequently, the lithium battery set 530 of the lithium battery module 500 fails to output electric energy to the electronic device through the positive terminal (+) and the negative terminal (−).
From the above discussions, if the residual charge quantity of the battery module is lower than the threshold charge quantity, the lithium battery module fails to output charge energy to the electronic device through the positive terminal (+) and the negative terminal (−). Meanwhile, even if the battery module is plugged into the electronic device, there is no detecting mechanism to judge whether the battery module is plugged or unplugged according to the positive terminal (+) and the negative terminal (−). Moreover, the conventional battery detector fails to be applied to such a battery module.
Therefore, there is a need of providing a battery status detection method and a battery status detection apparatus so as to obviate the conventional drawbacks.